CN104758093A - Analyzing method based on ANSYS/Workbench artificial heart valve mechanical property optimization - Google Patents

Abstract

The invention discloses an analyzing method based on ANSYS/Workbench artificial heart valve mechanical property optimization. The method is based on heart valve fluid dynamics and illuminates the theory that a fluid domain (blood) and a slid domain (artificial heart valve) couples with each other, and by establishing a fluid-solid coupled finite element model of biovalve, the fluid-solid coupled analysis of the biovalve is conducted. A natural heart valve configuration of a human body serves as an archetype, valve leaflet reference molded surfaces of a current research field are combined, and four rotating surfaces, namely a ball surface, a cylindrical surface, a paraboloid of revolution and an ellipsoidal surface are selected as the archetype reference surfaces of the biovalve. The analyzing method for analyzing the advantages and disadvantages of mechanical property of different biovalve valve shapes is provided.

Description

A kind of analytical method optimized based on ANSYS/Workbench artificial heart valve film dynamic performance

Technical field

The present invention relates to a kind of analytical method optimized based on ANSYS/Workbench artificial heart valve film dynamic performance.

Background technology

The pathological changes of heart lobe valve will damage hemodynamic performance, affect the blood circulation of human normal.After adopting the successful surgery of artificial valve replacement performances not conscience lobe since 1960, existing up to ten million patient has carried out displacement cardiac valve procedure, thus extends patient's life-span.Because biovalve has good hemodynamics performance, the advantage such as the probability not needing to take anticoagulant and thromboembolism is all the life low, is used widely in clinical.For many years, research worker are devoted to develop the more excellent heart lobe of performance always, but the function of current bioprosthetic valve and native heart valve still also exist bigger difference.After patient replaces heart lobe, the structure degradation due to biovalve makes heart lobe damage thus reduce valvular service life.It is the one of the main reasons of biovalve structure degradation that stress is concentrated.

Therefore, coupled problem between analyzing blood and biovalve, optimize the configuration of biovalve, the stress distribution etc. of detailed understanding heart lobe, this has very important theory value and realistic meaning to the understanding reason of valve failure, the optimal design of valve geometric parameter.

Summary of the invention

The present invention is in order to solve the problem, propose a kind of analytical method optimized based on ANSYS/Workbench artificial heart valve film dynamic performance, this method with heart lobe hydrodynamics for foundation, illustrate the theory that fluid domain (blood) intercouples with solid domain (Cardiac valve prosthesis), by building the indirect fluid-solid coupling model of biovalve, carry out the wind-structure interaction of biovalve.Prototype is configured as with the natural heart lobe of human body, in conjunction with the lobe leaf reference profile of current research field, select Surface of Sphere, the face of cylinder, the paraboloid of revolution and ellipsoid four kinds of surface of revolutions to be the biovalve prototype plane of reference, the invention provides the analytical method analyzing different biovalve lobe type mechanical property quality.

To achieve these goals, the present invention adopts following technical scheme:

Based on the analytical method that ANSYS/Workbench artificial heart valve film dynamic performance is optimized, comprise the following steps:

(1) intercouple based on fluid domain and solid domain, build fluid governing equation, solid governing equation, determine fluid structurecoupling interface, calculate the power acted on valve lobe leaf;

(2) based on ANSYS/Workbench, the analysis of fluid structurecoupling dynamic mechanical is carried out to the interaction between blood and three lobe leaves;

(3) with Surface of Sphere, the face of cylinder, the paraboloid of revolution and ellipsoid four kinds of surface of revolutions for the biovalve prototype plane of reference, analyze the mechanical property of different biovalve configuration, and contrast.

In described step (1), because solid domain and fluid domain do not exist lap in space, therefore fluid structure interaction can only be there is on the interface of lobe leaf and blood, because the ability that valve itself does not initiatively shrink, the opening and closing of lobe leaf depends on that blood and lobe ring stretch to the traction force of lobe leaf completely, the theory that fluid domain and solid domain intercouple illustrates masterpiece at coupling surface upper reaches body node for solid node, thus promotes the motion of solid.

In described step (1), the method building fluid governing equation is:

Blood is incompressible liquid, therefore the fluid domain of blood adopts incompressible Navier – Stokes fluid governing equation to describe: ^:

$\stackrel{\→}{\▿}\·\stackrel{\→}{u}=0$

$\mathrm{\ρ}(\frac{\∂\stackrel{\→}{u}}{\∂t}+\stackrel{\→}{u}\·\stackrel{\→}{\▿}\stackrel{\→}{u})=-\stackrel{\→}{\▿}p+\mathrm{\μ}{\▿}^2\stackrel{\→}{u}+\stackrel{\→}{F}$

In above formula for the velocity vector of any point in blood; ρ is density of blood; μ is the viscosity of blood; P is the pressure of blood; F is the body force (human body is supplied to blood) acting on blood; T is the time; for the gradient operator of current configuration;

In order to simplify calculating, nondimensionalization is carried out to above formula:

$\stackrel{\→}{\▿}\·\stackrel{\→}{u}=0$

$\frac{\∂\stackrel{\→}{u}}{\∂t}+\stackrel{\→}{u}\·\stackrel{\→}{\▿}\stackrel{\→}{u}=-\stackrel{\→}{\▿}p+\frac{1}{\mathrm{Re}}{\▿}^2\stackrel{\→}{u}+\stackrel{\→}{f}$

In above formula, Re is Reynolds number, Re=ρ _fuL/ η, U are the flow velocity of fluid; ρ _ffor fluid density; η is viscosity coefficient, and L is characteristic length, and f is the body force that human body acts on blood.

In described step (1), the concrete grammar building solid governing equation is:

What solid governing equation described is the distortion of solid under hydrokinetic effect, for the problem of blood with valve, defines solid and valve is nonlinear elastic material, the stressed equation of valve:

$\frac{{\mathrm{\ρ}}_s}{{\mathrm{\ρ}}_f}\stackrel{\stackrel{\·\·}{\→}}{x}-\mathrm{Div}{\underset{\‾}{\mathrm{\σ}}}_s=\stackrel{\→}{b}$

ρ in above formula _sfor the density of solid; ρ _ffor density of blood; for the acceleration of solid; σ _sfor the stress tensor of structure; for acting on the body force of solid.

In described step (1), determine that the method at fluid structurecoupling interface is:

The interaction part of fluid and solid is coupling surface Γ _sf, coupling surface has speed seriality and surface force seriality, therefore, and the position of coupling surface:

In above formula for horizontal domain set domain, for the displacement of lobe leaf.

The speed of coupling surface and acceleration:

${\stackrel{\→}{u}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}={\stackrel{\→}{x}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}$

In above formula for the speed of blood on coupling surface; for the displacement of coupling surface epivalve leaf,

${\stackrel{\→}{a}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}={\stackrel{\stackrel{\·\·}{\→}}{x}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}$

In above formula for the acceleration of blood on coupling surface,

${\underset{\‾}{\mathrm{\σ}}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}\·\stackrel{\→}{n}={\underset{\‾}{\mathrm{\σ}}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}\stackrel{\→}{n}$

In above formula, σfor stress tensor; for the local approach vector of coupling surface, subscript s and f represents solid and fluid respectively.

In described step (2), concrete grammar comprises:

A. PRO/E is used to carry out d solid modeling to biovalve lobe leaf and arterial wall;

B. use ANSYS/Workbench program, the data according to the stress-strain curve of the fresh bio valvular tissue material measured define valvular material;

C. biovalve lobe leaf and arterial wall model imported Workbench program with the form of IGES and carry out stress and strain model, obtaining fluid structurecoupling dynamic mechanical analysis FEM (finite element) model;

D. the parameter provided according to medical research applies fluid structurecoupling boundary condition;

E. by indirect fluid-solid coupling analytical calculation, the stress distribution situation of Cardiac valve prosthesis lobe leaf and the motion conditions of blood is drawn.

The concrete grammar of described step (3) is:

A. four kinds of lobe airfoil surfaces are all analyzed according to the step of A, B, C, D in step (2);

B. by indirect fluid-solid coupling analytical calculation, draw the distribution situation of the maximum principal stress of Cardiac valve prosthesis lobe leaf, equivalent stress and the maximum shear stress, and analysis contrast is carried out to four kinds of valve configuration mechanical properties.

Beneficial effect of the present invention is: the present invention for foundation, utilizes finite element software to carry out fluid structurecoupling dynamics simulation for biovalve with heart lobe Hydrodynamics Theory, draws pressure curve and the rate curve of blood, also has the stress distribution of biovalve lobe leaf.Four kinds of lobe leaf configurations for biovalve carry out the analysis contrast of maximum principal stress, equivalent stress and the maximum shear stress distributed areas and size, thus reach a conclusion: stress concentration phenomenon be mainly distributed in the region crossing with stitching border in conjunction with limit of lobe leaf and lobe leaf in conjunction with central area, limit.Face of cylinder mechanical property is in every respect all poor, and the paraboloid of revolution, Surface of Sphere and ellipsoid have respective advantage at different aspect, and this is that the biovalve developing function admirable provides foundation.

Accompanying drawing explanation

Fig. 1 (a) is Surface of Sphere type lobe leaf moulding schematic diagram;

Fig. 1 (b) is Surface of Sphere type lobe leaf moulding schematic diagram;

Fig. 1 (c) is Surface of Sphere type lobe leaf moulding schematic diagram;

Fig. 2 (a) is face of cylinder type lobe leaf moulding schematic diagram;

Fig. 2 (b) is face of cylinder type lobe leaf moulding schematic diagram;

Fig. 2 (c) is face of cylinder type lobe leaf moulding schematic diagram;

Fig. 3 (a) is paraboloid of revolution type lobe leaf moulding schematic diagram;

Fig. 3 (b) is paraboloid of revolution type lobe leaf moulding schematic diagram;

Fig. 3 (c) is paraboloid of revolution type lobe leaf moulding schematic diagram;

Fig. 4 (a) is ellipsoid type lobe leaf moulding schematic diagram;

Fig. 4 (b) is ellipsoid type lobe leaf moulding schematic diagram;

Fig. 4 (c) is ellipsoid type lobe leaf moulding schematic diagram;

Fig. 5 (a) is lobe leaf lobe hole modeling parameters schematic diagram;

Fig. 5 (b) is lobe leaf lobe hole physical model schematic diagram;

Fig. 6 (a) is biovalve fluid structurecoupling physical model schematic diagram;

Fig. 6 (b) is biovalve indirect fluid-solid coupling model schematic;

Fig. 7 is the stress-strain curve figure of biological valvular tissue material;

Fig. 8 is Blood Model entrance, outlet and the definition of fluid structurecoupling face;

Fig. 9 is lobe limb circle conditional definition;

Figure 10 is the blood velocity profile of sampled point;

Figure 11 is the blood pressure curve chart of sampled point;

Figure 12 is the time dependent Stress Map of valve;

Figure 13 (a) is four kinds of profile lobe leaf equivalent stress cloud atlas during 0.022s;

Figure 13 (b) is four kinds of profile lobe leaf equivalent stress cloud atlas during 0.044s;

Figure 13 (c) is four kinds of profile lobe leaf equivalent stress cloud atlas during 0.067s;

Figure 13 (d) is four kinds of profile lobe leaf equivalent stress cloud atlas during 0.089s;

Figure 14 (a) is four kinds of profile lobe leaf maximum principal stress Stress Map during 0.2222s;

Figure 14 (b) is four kinds of profile lobe leaf maximum principal stress Stress Map during 0.4444s;

Figure 14 (c) is four kinds of profile lobe leaf maximum principal stress Stress Map during 0.6667s;

Figure 14 (d) is four kinds of profile lobe leaf maximum principal stress Stress Map during 0.8889s;

Figure 15 (a) is four kinds of profile lobe leaf the maximum shear stress cloud atlas during 0.2222s;

Figure 15 (b) is four kinds of profile lobe leaf the maximum shear stress cloud atlas during 0.4444s;

Figure 15 (c) is four kinds of profile lobe leaf the maximum shear stress cloud atlas during 0.6667s;

Figure 15 (d) is four kinds of profile lobe leaf the maximum shear stress cloud atlas during 0.8889s.

Detailed description of the invention:

Below in conjunction with accompanying drawing and embodiment, the invention will be further described.

Based on the biovalve fluid structurecoupling mechanics property analysis of ANSYS, step is as follows:

A.1. the Geometric Modeling of (1) biovalve lobe leaf

In the process of the lobe leaf modeling of biovalve, we are with the acquiescence Cartesian coordinate initial point of Pro/E software for modeling initial point O, and the geometric equation according to each surface of revolution (Surface of Sphere, the face of cylinder, the paraboloid of revolution and ellipsoid) creates surface of revolution.Be parallel to Z axis (13,0, z) straight line is rotating shaft, makes the taper seat of the minimum point B of over-rotation curved surface, and the semiapex angle α of taper seat is 3 °.Taper seat is crossing with four kinds of surface of revolutions, draws intersection.XOZ plane with the rotating shaft of taper seat for axis tilt the peak that the plane formed and intersection point A and A ' of intersection are monolithic lobe leaf.The intersection points B of intersection and Z axis is the minimum point of monolithic lobe leaf.The intersection point of surface of revolution and circular cone axis is the minimum point of monolithic lobe leaf free margins.The angle of AC and X-axis is the angle β of lobe leaf free margins and joint portion plane.And the difference of the Z coordinate of A point and B point is the height H of lobe leaf or lobe frame.After the parametric modeling of biovalve, above-mentioned geometric parameter can obtain.

1, Surface of Sphere is as the parameter model with reference to face:

As Fig. 1 (a)-Fig. 1 (c), with the acquiescence Cartesian coordinate initial point of Pro/E software for modeling initial point O, creating radius is the Surface of Sphere of 13.4mm, and the equation of Surface of Sphere is x ²+ y ²+ z ²=13.4 ².Cross (0,0 ,-13.4) and make (x-13) ²+ y ²=[13+ (z+13.4) tan α)] ²taper seat, wherein α=3 °.According to the modeling procedure of lobe leaf, obtain the monolithic lobe leaf model of the biovalve designed for reference plane with Surface of Sphere, monolithic lobe leaf is carried out circumferential array using the rotating shaft of taper seat as central shaft, then obtains three entity bioprosthetic valve leaves.

2, the face of cylinder is as the parameter model with reference to face:

As Fig. 2 (a)-Fig. 2 (c), with the acquiescence Cartesian coordinate initial point of Pro/E software for modeling initial point O, creating equation is ${(x\cos \frac{\mathrm{\π}}{4}-z\sin \frac{\mathrm{\π}}{4})}^2+y^2={13}^2$ The face of cylinder, mistake do taper seat, wherein α=3 °.According to the modeling procedure of lobe leaf, obtain the monolithic lobe leaf model of the biovalve designed for reference plane with the face of cylinder, monolithic lobe leaf is carried out circumferential array using the rotating shaft of taper seat as central shaft, then obtains three entity bioprosthetic valve leaves.

3, the paraboloid of revolution is as the parameter model with reference to face:

As Fig. 3 (a)-Fig. 3 (c), with the acquiescence Cartesian coordinate initial point of Pro/E software for modeling initial point O, according to parametric equation x=13 × t, y=0, z=(13 × t) ²/ 13 create x ²the parabola of=13z take Z axis as rotating shaft, and establishment equation is x ²+ y ²the paraboloid of revolution of=13z.Cross (0,0,0) and make (x-13) ²+ y ²=(13+ztg α) ²taper seat, wherein α=3 °.According to the modeling procedure of lobe leaf, obtain the monolithic lobe leaf model of the biovalve designed for reference plane with the paraboloid of revolution, monolithic lobe leaf is carried out circumferential array using the rotating shaft of taper seat as central shaft, then obtains three entity bioprosthetic valve leaves.

4, ellipsoid is as the parameter model with reference to face:

As Fig. 4, with the acquiescence Cartesian coordinate initial point of Pro/E software for modeling initial point O, creating equation is ellipsoid, wherein a=13.4, b=14.8.Crossing (0,0 ,-14.8) as equation is taper seat, central shaft is x=13, α=3 °.In this model, ellipsoid equation is taper seat equation is (x-13) ²+ y ²=[13+ (z+14.8) tg α] ².According to the modeling procedure of lobe leaf, obtain the monolithic lobe leaf model of the biovalve designed for reference plane with ellipsoid, monolithic lobe leaf is carried out circumferential array using the rotating shaft of taper seat as central shaft, then obtains three entity bioprosthetic valve leaves.

By the systematic parameter of Pro/E software, can draw the precise geometrical parameter of the lobe leaf model designed, the physical dimension parameter of the biovalve model of four kinds of different profiles is as shown in table 1.

The physical dimension parameter of the biovalve model of table 1 four kinds of different profiles

(2) the human aortic parameter that provides according to Qianfo Mount hospital of this research is as Fig. 5, in PRO/E, three-dimensional reconstruction is carried out to tremulous pulse hole, getting three lobe leaves in conjunction with the plane at mid point place, limit is datum plane, setting up distance datum plane distance successively according to image scanning parameter is 6mm, 12.24mm, the datum plane of 18mm and 24mm, on the datum plane of correspondence with the geometric center of three lobe leaves for initial point draws corresponding diameter successively for 35.52mm, 38.64mm, 120 ° of circular arcs of 30.24mm, obtain carrying out curve fitting after grass plots, application boundary mixing order also obtains the threedimensional model of lobe hole as shown in Figure 5 after geometric array.

(3) the indirect fluid-solid coupling model modeling of bioprosthetic valve

The indirect fluid-solid coupling model of bioprosthetic valve comprises the coupling surface of the solid domain of lobe leaf and arterial wall, the fluid domain of blood and lobe leaf and blood.Under the physiological environment of human body, be dispersed with blood around cardiac valve, under the impact of blood, realize the keying of valve.In conjunction with actual, in this time sunykatuib analysis, we think and are full of blood in the active lobe hole of arterial wall and blood vessel.If the entrance of arterial wall and outlet are closed and carried out hypostazation, can think that whole arterial wall model is fluid model.What adopt in the present invention is carry out solid modelling with in PRO/E.With the form of IGES, the modeling in PRO/E is imported in ANSYS, and carry out stress and strain model, obtain indirect fluid-solid coupling model.

Fig. 6 is the physical model and the FEM (finite element) model that import the valve after ANSYS.

2, material properties

At present conventional biovalve material is the aortic valve of pig and bovine pericardial material mainly, and their main material is cardiac muscle fiber, and cardiac muscle fiber is a kind of nonlinear cohesive material.This kind of characteristic of material should be taken into full account when simulating biovalve.This analysis carrys out definition material according to the data of the stress-strain curve of the fresh bio valvular tissue material measured, and stress-strain curve as shown in Figure 7.

3, boundary condition is applied

In conjunction with the practical situation of biovalve work, the coupling surface that we define blood and lobe leaf is the upper and lower surface of three biovalve lobe leaves and the cross section of lobe leaf free margins through-thickness, and it is fluid structurecoupling face that known three lobe leaves have 9 faces.The import and export in convection cell territory are arranged, and in the setting of blood entry port boundary condition, the speed according to clinical data setting fluid is 1m/s, and in the setting of blood export boundary condition, pressure is set to 0, as shown in Figure 8.

Because biovalve lobe leaf is made up of porcine aortic valve or bovine pericardium, biovalve lobe leaf material belongs to elastic material.According to the data that the cardiac valve room of Shandong ProvinceQianfoshan Hospital provides, lobe leaf material is the material of homogenizing uniform thickness, and thickness is 0.45mm.

Biovalve lobe frame material adopts titanium alloy, and its hardness far above lobe leaf material, thus will be supposed that the characteristic of lobe frame is perfect rigidity, ignore the distortion of lobe frame.Now lobe limb edge AC is attached on lobe frame securely, and on AC limit, the motion vector of each point is zero, applies staff cultivation to AC limit.AB and BC is free margins, as shown in Figure 9.

4. biovalve wind-structure interaction

(1) dynamic analysis of blood

In experimental analysis, consider that Tricuspid valve answers mechanical change under the action period under blood impacts.In fluid analysis, setting blood entry port speed is 1m/s, and outlet is set as that pressure is zero, and the density of blood is set as 0.98g/cm ³.

By the setting of fluid modules in ANSYS, be fluid blood by arterial wall enclose inside, the kinestate of single blood particles can be obtained after definition material attribute, grid division, applying boundary condition and post processing, in order to the simplicity that we observe, we choose single particle ten kinds of moment in whole motor process and obtain the blood velocity profile of sampled point as Figure 10.Then we obtain the blood pressure curve chart of sampled point as Figure 11 according to same way.

Can clearly be seen by the speed curve diagram of blood, when the time is 0.4s, the speed of blood is maximum, the blood pressure of the single particle now chosen is also in maximum, then owing to causing the increase with pressure that weakens of speed after the touching of blood and lobe leaf, when blood is completely by after lobe leaf, the speed of blood starts to rise, because it is zero that the outlet of arterial wall is set to pressure, so can know and see that blood is on a declining curve after by lobe leaf, until reduce to zero in outlet pressure.

(2) dynamic analysis of lobe leaf

The time dependent Stress Map of valve is as Figure 12, even in the stress distribution analyzing initial stage lobe leaf, the region crossing with stitching border in conjunction with limit of lobe leaf and lobe leaf all there occurs stress concentration phenomenon in conjunction with central area, limit.The joining edge of lobe leaf is stressed relative to the abdominal part of lobe leaf comparatively large, and the stress concentration phenomenon at this place may make lobe leaf be damaged, and causes lobe leaf to shorten service life.To consider when designing valve the concentrated region of stress easily occurs, reducing or prevent stress concentration phenomenon thus avoid lobe leaf to damage, improving the durability of lobe leaf.

B. different lobe airfoil surface is to the impact analysis of biovalve dynamic mechanical

Desirable bioprosthesis valve moulding should meet the properties requirement of natural heart lobe, but these require often restriction mutually, can not meet optimum simultaneously.Analysis contrast is carried out with reference to profile using ball profile, ellipsoid profile, rotary parabolic profile and cylinder profile as lobe leaf.

(1) different lobe airfoil surface equivalent stress is analyzed

Utilize finite element analysis software to carry out sunykatuib analysis, blood impact under ball profile, ellipsoid profile, rotary parabolic profile and cylinder profile lobe leaf equivalent stress over time Stress Map as shown in Figure 13 (a)-Figure 13 (d).

Stress distribution cloud atlas is from the graph known, and when 0.022s, comparatively high-stress area has all appearred in four kinds of profiles, ball profile, ellipsoid and paraboloid of revolution lobe leaf be distributed in intersection in conjunction with limit and joining edge compared with high-stress area territory.The face of cylinder at lobe leaf in conjunction with the central area on limit and the intersection in conjunction with limit and joining edge.When 0.044s, ball profile turn increases the central area of lobe leaf in conjunction with limit with paraboloid of revolution lobe leaf compared with high-stress area territory, the face of cylinder comparatively high-stress area territory at lobe leaf in conjunction with limit having occurred again two regions, place.When 0.066s, the comparatively high-stress area territory of paraboloid of revolution lobe leaf at lobe leaf in conjunction with limit turn increasing two places.Along with the increase of time, these regions increase gradually.The stress of the face of cylinder and the paraboloid of revolution is concentrated and is mainly distributed in lobe leaf in conjunction with the central area on limit and the intersection in conjunction with limit and joining edge.Ellipsoid and Surface of Sphere are mainly distributed in the intersection in conjunction with limit and joining edge of lobe leaf.

The stress concentration distribution situation of lobe leaf is drawn according to the STRESS VARIATION cloud atlas of above-mentioned four kinds of profile lobe leaves:

The stress concentration distribution situation of table 2 different profile lobe leaf

Comparatively speaking the region of stress concentration on the face of cylinder is comparatively large, and the paraboloid of revolution takes second place, and stress is concentrated and lobe leaf can be caused tired, thus makes the calcification of lobe leaf, causes valve failure.Can find out that the stress distribution of four kinds of lobe types is all uneven, the maximum region of stress is all the intersections in conjunction with limit and joining edge at lobe leaf, very easily tearing of valve occurs herein, causes lobe leaf to lose efficacy.From this angle, the lobe leaf dynamic mechanical of ellipsoid and Surface of Sphere is much better.

But from the stress that lobe leaf is subject to, Surface of Sphere is stressed maximum, takes second place in the face of cylinder, and ellipsoid is stressed minimum.

(2) different lobe airfoil surface maximum principal stress is analyzed

Utilize finite element analysis software to carry out sunykatuib analysis, under the impact of blood, the lobe leaf of ball profile, ellipsoid, rotary parabolic profile and cylinder profile is along with the Stress Map of time variations is as shown in Figure 14 (a)-Figure 14 (d).

Above-mentioned simulation is analyzed for the different configurations of lobe leaf, draws the maximum principal stress of lobe leaf as table 3 according to the STRESS VARIATION cloud atlas of above-mentioned four kinds of profile lobe leaves:

The maximum principal stress of table 3 different profile lobe leaf

Can find out from the graph, the maximum principal stress skewness phenomenon of ellipsoid and face of cylinder lobe leaf is comparatively obvious, and the paraboloid of revolution takes second place, the maximum principal stress distribution uniform of Surface of Sphere.Maximum principal stress skewness can cause the distortion along lobe leaf uneven, causes lobe leaf to be easily damaged.Smaller with ellipsoid of the maximum principal stress maximum of four kinds of profiles, the paraboloid of revolution takes second place, and is then Surface of Sphere.Relative to other profiles, maximum principal stress mechanical property in its value and stress distribution on the face of cylinder is all poor.

(3) the maximum shear stress analysis of different lobe airfoil surface

Utilize finite element analysis software to carry out sunykatuib analysis, under the impact of blood, the lobe leaf of ball profile, ellipsoid profile, rotary parabolic profile and cylinder profile is along with the cloud atlas of time variations is as Figure 15 (a)-Figure 15 (d).

From stress distribution cloud atlas, the stress distribution of four kinds of lobe types is all uneven, and the maximum region of stress is all at the intersection in conjunction with limit and joining edge of lobe leaf.The region of stress concentration of Surface of Sphere lobe leaf is distributed in the intersection in conjunction with limit and joining edge, the region of stress concentration of the face of cylinder and paraboloid of revolution lobe leaf at lobe leaf in conjunction with the central area on limit and the intersection in conjunction with limit and joining edge.Comparatively speaking the region of stress concentration on the face of cylinder is comparatively large, and the paraboloid of revolution takes second place, and the stress distribution of Surface of Sphere is more relatively uniform.But from the stress that lobe leaf is subject to, Surface of Sphere is stressed maximum, takes second place in the face of cylinder, and ellipsoid is stressed minimum.

The com-parison and analysis of (4) four kinds of lobe airfoil surface mechanical properties

Can be found out by the equivalent stress of four kinds of profile lobe leaves, shear stress and distribution of principal stress cloud atlas, all there is stress distribution non-uniform phenomenon in various degree in four kinds of profile lobe leaves, region of stress concentration is slightly different.When analyzing equivalent stress, ellipsoid and Surface of Sphere stress concentration phenomenon are mainly distributed in the intersection in conjunction with limit and joining edge of lobe leaf, and the face of cylinder and the paraboloid of revolution are also distributed in the central area of lobe leaf in conjunction with limit, wherein the stress concentration phenomenon on the face of cylinder is the most serious.Equivalent stress maximum region is all the intersections in conjunction with limit and joining edge at lobe leaf.But from the stress value analysis that lobe leaf is subject to, Surface of Sphere is stressed maximum, takes second place in the face of cylinder, and ellipsoid is stressed minimum.When analyzing principal stress, stress maximum all appears at the central area of free margins, and comparatively greatly, Surface of Sphere is comparatively even for the face of cylinder and the uneven region of ellipsoid stress distribution.But from the stress value analysis that lobe leaf is subject to, the face of cylinder is stressed maximum, and Surface of Sphere takes second place, and ellipsoid is stressed minimum.When analyzing shear stress, ellipsoid and Surface of Sphere stress concentrate the intersection in conjunction with limit and joining edge being mainly distributed in lobe leaf, and the face of cylinder and paraboloid of revolution distributed areas are comparatively greatly, and wherein the stress concentration phenomenon on the face of cylinder is the most serious.But from the stress value analysis that lobe leaf is subject to, Surface of Sphere is stressed maximum, takes second place in the face of cylinder, and ellipsoid is stressed minimum.From above-mentioned analysis, face of cylinder mechanical property is in every respect all poor, and the paraboloid of revolution, Surface of Sphere and ellipsoid have respective advantage at different aspect, analyze mainly for the paraboloid of revolution, Surface of Sphere and ellipsoid in the design optimization after lobe leaf.

By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.

Claims (7)

1., based on the analytical method that ANSYS/Workbench artificial heart valve film dynamic performance is optimized, it is characterized in that: comprise the following steps:

(1) intercouple based on fluid domain and solid domain, build fluid governing equation, solid governing equation, determine fluid structurecoupling interface, calculate the power acted on valve lobe leaf;

(2) based on ANSYS/Workbench, the analysis of fluid structurecoupling dynamic mechanical is carried out to the interaction between blood and three lobe leaves;

(3) with Surface of Sphere, the face of cylinder, the paraboloid of revolution and ellipsoid four kinds of surface of revolutions for the biovalve prototype plane of reference, analyze the mechanical property of different biovalve configuration, and contrast.

2. analytical method as claimed in claim 1, it is characterized in that: in described step (1), because solid domain and fluid domain do not exist lap in space, therefore fluid structure interaction can only be there is on the interface of lobe leaf and blood, because the ability that valve itself does not initiatively shrink, the opening and closing of lobe leaf depends on that blood and lobe ring stretch to the traction force of lobe leaf completely, the theory that fluid domain and solid domain intercouple illustrates masterpiece at coupling surface upper reaches body node for solid node, thus promotes the motion of solid.

3. analytical method as claimed in claim 1, is characterized in that: in described step (1), and the method building fluid governing equation is:

Blood is incompressible liquid, therefore the fluid domain of blood adopts incompressible Navier – Stokes fluid governing equation to describe::

$\stackrel{\→}{\▿}\·\stackrel{\→}{u}=0$

$\mathrm{\ρ}(\frac{\∂\stackrel{\→}{u}}{\∂t}+\stackrel{\→}{u}\·\stackrel{\→}{\▿}\stackrel{\→}{u})=-\stackrel{\→}{\▿}p+\mathrm{\μ}{\▿}^2\stackrel{\→}{u}+\stackrel{\→}{F}$

In above formula for the velocity vector of any point in blood; ρ is density of blood; μ is the viscosity of blood; P is the pressure of blood; F is the body force acting on blood, and human body is supplied to blood; T is the time; for the gradient operator of current configuration;

In order to simplify calculating, nondimensionalization is carried out to above formula:

$\stackrel{\→}{\▿}\·\stackrel{\→}{u}=0$

$\frac{\∂\stackrel{\→}{u}}{\∂t}+\stackrel{\→}{u}\·\stackrel{\→}{\▿}\stackrel{\→}{u}=-\stackrel{\→}{\▿}p+\frac{1}{\mathrm{Re}}{\▿}^2\stackrel{\→}{u}+\stackrel{\→}{f}$

In above formula, Re is Reynolds number, Re=ρ _fuL/ η, U are the flow velocity of fluid; ρ _ffor fluid density; η is viscosity coefficient, and L is characteristic length, and f is the body force that human body acts on blood.

4. analytical method as claimed in claim 1, is characterized in that: in described step (1), and the concrete grammar building solid governing equation is:

What solid governing equation described is the distortion of solid under hydrokinetic effect, for the problem of blood with valve, defines solid and valve is nonlinear elastic material, the stressed equation of valve:

$\frac{{\mathrm{\ρ}}_s}{{\mathrm{\ρ}}_f}\stackrel{\stackrel{..}{\→}}{x}-\mathrm{Div}{\underset{\‾}{\mathrm{\σ}}}_s=\stackrel{\→}{b}$

ρ in above formula _sfor the density of solid; ρ _ffor density of blood; for the acceleration of solid; σ _sfor the stress tensor of structure; for acting on the body force of solid.

5. analytical method as claimed in claim 1, is characterized in that: in described step (1), determines that the method at fluid structurecoupling interface is:

The interaction part of fluid and solid is coupling surface Γ _sf, coupling surface has speed seriality and surface force seriality, therefore, and the position of coupling surface:

In above formula for horizontal domain set domain, for the displacement of lobe leaf.

The speed of coupling surface and acceleration:

${\stackrel{\→}{u}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}={\stackrel{\→}{x}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}$

In above formula for the speed of blood on coupling surface; for the displacement of coupling surface epivalve leaf,

${\stackrel{\→}{a}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}={\stackrel{..}{\stackrel{\→}{x}}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}$

In above formula for the acceleration of blood on coupling surface,

${\underset{\‾}{\mathrm{\σ}}}_s{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}\·\stackrel{\→}{n}={\underset{\‾}{\mathrm{\σ}}}_f{|}_{{\mathrm{\Γ}}_{\mathrm{sf}}}\stackrel{\→}{n}$

In above formula, σfor stress tensor; for the local approach vector of coupling surface, subscript s and f represents solid and fluid respectively.

6. analytical method as claimed in claim 1, is characterized in that: in described step (2), concrete grammar comprises:

A. PRO/E is used to carry out d solid modeling to biovalve lobe leaf and arterial wall;

B. use ANSYS/Workbench program, the data according to the stress-strain curve of the fresh bio valvular tissue material measured define valvular material;

C. biovalve lobe leaf and arterial wall model imported Workbench program with the form of IGES and carry out stress and strain model, obtaining fluid structurecoupling dynamic mechanical analysis FEM (finite element) model;

D. the parameter provided according to medical research applies fluid structurecoupling boundary condition;

E. by indirect fluid-solid coupling analytical calculation, the stress distribution situation of Cardiac valve prosthesis lobe leaf and the motion conditions of blood is drawn.

7. analytical method as claimed in claim 1, is characterized in that: the concrete grammar of described step (3) is:

A. four kinds of lobe airfoil surfaces are all analyzed according to the step of A, B, C, D in step (2);

B. by indirect fluid-solid coupling analytical calculation, draw the distribution situation of the maximum principal stress of Cardiac valve prosthesis lobe leaf, equivalent stress and the maximum shear stress, and analysis contrast is carried out to four kinds of valve configuration mechanical properties.